It is possible that the main title of the report Marfan Syndrome is not the name you expected. Please check the synonyms listing to find the alternate name(s) and disorder subdivision(s) covered by this report.
As Jenny points out, being able to lisp the alphabet song at age two has little to do with 'knowing' the alphabet. And, yes, most children learn the letters by sight and sound in kindergarten, although most are capable of learning this information sooner if diligently taught by parents or others.
For some kids, this Alphabet Book was literally the only thing they could read, but it was that teeny, tiny piece they needed to grow confidence and build a solid foundation of literacy learning and phonological awareness. By the time they finished with letters X, Y, and Z, they memorized the first half of the book.